Joseph Koshakow <koshy44@gmail.com> writes:
> There's a rare edge case in `alter table` that can prevent users from
> dropping a column as shown below
> # create table atacc1(a int, "........pg.dropped.1........" int);
> CREATE TABLE
> # alter table atacc1 drop column a;
> ERROR: duplicate key value violates unique constraint
> "pg_attribute_relid_attnam_index"
> DETAIL: Key (attrelid, attname)=(16407, ........pg.dropped.1........)
> already exists.
I think we intentionally did not bother with preventing this,
on the grounds that if you were silly enough to name a column
that way then you deserve any ensuing problems.
If we were going to expend any code on the scenario, I'd prefer
to make it be checks in column addition/renaming that disallow
naming a column this way. What you propose here doesn't remove
the fundamental tension about whether this is valid user namespace
or not, it just makes things less predictable.
regards, tom lane